"dimmer switch" doesnt work(and other issues)

so, this isnt my truck, im on here trying to help my brother solve some problem with his truck.

he bought the truck from someone and they had a non-work radio(bad fuse) and A LOT of electrical problems...

they mostly revolve around the dimmer switch(which was replaced according to the previous owner), and the problems are like, the dome light is "always on" and when you try to use the dimmer to turn it off the light turns off for a fraction of a second on the click over from on/off.

we assumed it was the door jam switch causing the problem, and was recommended to take the switches out which should take the switch out of play when it comes to turning the light on, that didn't work.

and that really as far as we got to solving that issue, since we cant afford a new 80$ dimmer switch at the whim of it possibly being the problem, im hoping someone knows some better troubleshooting tips to narrow down the problem.(have asked a few mechanics, they all point to "have us fix it for you")

(the dimmer switch also controls headlights, yet the headlight DO turn on and off)

another issue is(atleast i believe this is an issue) is that the light around the ignition is always on, i don't know if thats normal but am worried it could kill the battery.

p.s it seems the radio 12V+ line has been re-ran because the fuze for the radio is not the one indicated in the manual(its now ran into the same fuse as the dome light)

-thanks in advance, i'm not great in automotive, so pardon me if im not seeming clear-

to me you have separate issues.. the dome light issue sounds like a headlight switch issue.. it may be the one for the optional cargo light. as far as the ignition ring i have no clue. mine doesnt have one. and the radio sound like someone really hacked it up to wire it and it may be back feeding to keep em on.. id first pull the radio at and see how big of a rats nest it has.

I actually think your problems might be together. Early dodges used a back strap for the radio ground.
Sometimes, when red necky guys change the radio out, they tie into the dimmer wire for ground. You didn't mention stock radio or not, but did say the power was re run.
Just something to check.

hey thanks for the quick replies, after reading your responses we were in the middle of having the dash taken apart so i decided to mess with the dimmer switch(headlight switch) to find out if it was the problem, i found out the master power(earliest shut off for dome light) is a yellow+ ylw/black- cable. and now i have a few question(to possibly solve my problem) on how the lights/door jams/ dimmer works...

1.) if the dimmer is turn to shut off the dome light, will the door jam switches turn it on?

2.) if i removed(unplug) the door jab switches from both door, would that make it = the door always being shut? or open?(lights on/off)


the reason i need to know #2 is it might just be the door jams, and #1 will show that door jams is the likely cause.

extra question, what(on an older car) would turna dome light on?(i know door jam, and dimmer switch, but thats it)